Hydraulically-actuated brake mechanism



Nov. 18, 930.

c. s. BRA GG ETAL HYDRAULIC ALLY ACTUATED BRAKEMEC HANISM 2 Sneaks-Sheet1.

Original File Aug- 20, I925 ATTORNEY a) S INVENTOR} Wm Y QQMF Nov. 18,1930. c. s. BRAGG ET AL HYDRAULICALLY ACTUATED BRAKE MECHANISM 2Shets-Sheef 2 Original Filed Aug- 20, 1925 Patented Nov. 18, 1930 UNITEDSTATES PATENT OFFICE CALEB S. BRAGG, 01 PALM BEACH, FLORIDA, AND VICTORW. KLIESRATH, I03! WASHINGTON, NEW YORK, ASSIGNORS TO BRAGG-KLIESRATHCORPORATION, OF LONG ISLAND CITY, NEW YORK, A CORPORATION OF NEW YORK.EYDRAULIOALLY-ACTUATED BRAKE MECHANISM Application filed. August 20,1925, Serial No. 51,300. Renewed October 13, 1988.

Our invention consists in the novel features hereinafter described,reference being had to the accompanying drawings which show oneembodiment selected by us for pur- 5 poses of illustration, and the saidinvent on is fully disclosed in the following description and claims.

Our invention consists in an improved bydraulic brake system, operatableeither by 1 means of a power actuator operated in any desired mannerunder the control of the operator, the power being supplied, forexample,

by suction from the intake manifold of an internal combustion engine,our improved system being especially adapted for use in connection withone or any number of brake mechanisms thereof.

In the operation of hydraulic brake mechanisms, it is important andnecessary that the system be kept full of oil at all times, whichnecessitates the addition of oil from time to time to make updeficiencies caused by leakage or otherwise. It is also important toprovide means for eliminating air occluded in the oil in order that thefull force of the main hydraulic piston may be applied through the lineor lines to the auxiliary hydraulic pistons which actuate brake mechaonisms, through a non-compressible medium. To this end the main hydrauliccylinder is preferably supported in a slightly inclined position, sothat when the main hydraulic piston is retracted, the portion of thecylinder adjacent thereto will be the highest portion, and we providesaid cylinder at this point with a port or ports communicating with theoil reservoir in such manner that a 40 large body of oil of greaterdiameter horizontally than said port or ports is maintained immediatelyadjacent thereto, said port or ports being located adjacent to the mainhydraulic piston, so that they will remain open when the said piston isin retracted or off posithe physical power of the operator, or bylllicsystem. It f0 In the arrangement of the various cylinders actuated bythe main hydraulic cylinder, it is'preferable to locate them below thelevel of the main cylinder, so that the port or ports above mentionedshall be not only at the hi hest point of the main hydrauliccylinderfimt also at the highest point of the hylows from thisarrangement that any occluded air in the systerm will gradually find itsway to the port or ports above mentioned, .or be collected in the mainhydraulic cylinder, closely adjacent thereto, so that the first movementof the main hydraulic piston will force out such collected air throughsaid port or ports into the large body of oil in the oil reservoir,ermitting it to escape in bubbles to the sur ace thereo It also followsthat when the main hydraulic piston returns to its normal or offposition in a short period of time, as for example after an applicationand release of the brakes, and opens the communicating port or portsabove referred to, clean oil, free from air, will enter the mainhydraulic cylinder to supply any deficiency therein caused by'thedisplaced air or oil, thus keeping the system automatically filled atall times, while providing for the discharge of occluded air.

Our invention also provides convenient means for effecting the ori 'nalfilling of the system, or the bleeding 0 the same, at any time whennecessary or desirable, as in the case of repair or adjustment of any ofthe hydraulic cylinders or connections. To this end we provide an oilreservoir which may be the same oil reservoir previously mentioned, or aseparate reservoir, as preferred, either independent of or connectedwith the first mentioned reservoir, and connected to the hydraulic lineextending from the main hydraulic cylinder to the cylinder or cylindersoperated thereby, and preferably closely adjacent to the main hydrauliccylinder,

by a pipe or passage in which is located a check valve for preventingthe return of oil to the reservoir, and a shut off valve by means ofwhich this connecting pipe or passage may be closed when desired. Bythis means, the system'may be filled initially, or at any time, and mayalso be bled whenever necessary, by opening the shut off valve andoperating the main hydraulic piston which will draw oil from thereservoir on the return stroke of the main hydraulic piston, and on thepower stroke thereof, will force it into the lines, the check valvepreventing the return of the oil to the rservoir, and this operation maybe repeated until the system is filled or bled. It is to be understoodthat the portion of the system to be filled or bled is open toatmosphere during the power stroke of the main piston, but is closed toatmos phere as by the fingers of the operator during the return strokethereof. The shut off valve may be closed when the system is filled orbled so as to prevent oil being drawn into the main hydraulic cylinderon the return movement of the piston after the application of the brakemechanism, as this would tend to pre--' vent the proper release of thebrake mechanism. We may, however, employ this initial filling mechanismin conjunction with the automatic filling mechanism previously referredto, with which it directly cooperates, in which case the shut ofi' valvemay be omitted, if desired, provided one oil reservoir is used orconnections made between reservoirs, if more than one is employed, asany surplus oil drawn in past the check valve in the communicating pipeor passage on the return movement of the main hydraulic piston, would bedisplaced through the previously mentioned ports or port connecting themain hydraulic cylinder with the oil reservoir, into said oil reservoirby the force of the retracting springs of the brake mechanism actingthrough the pistons which operate the brakes upon the oil in the system,and thereby returned to the reservoir.

It will be seen that the venting aperture which establishes a free andunobstructed communication in both directions between the liquidreservoir and the pressure cylinder and the entire hydraulic systemconnected therewith, enables the reservoir to act as an expansion tankinto which and from which the liquid can pass to accommodate thecontraction and expansion of the liquid of the entire system.

In the accompanying drawings which show an installation in an automotivevehicle embodying our present invention,

Fig. 1 is a diagrammatic view illustrating the chassis of an automotivevehicle, the hydraulic brake mechanism therefor, and a power actuator'for operating the main hydraulic piston, operated by suction from theintake manifold of an internal combustion en ine under the control ofthe operator.

ig. 2 is an enlarged sectional view of the actuator, the main hydrauliccylinder and piston and the oil reservoir and its connections with thesystem.

Fig. 3 is a vertical section on the line 3-3 of Fig. 2.

Referring to Fig. 1, 1 represents the chassis of an automotive vehicle,which is rovided in this instance with four wheel bra e mechanisms,indicated generally at 2, 2, 2, 2; the brake mechanisms themselves formno part of our present invention and may be of any usual or desiredtype. A hydraulic cylinder and piston are provided for the operation ofeach brake mechanism, the said brake cylinders being indicateddiagrammatically at 3, 3, 3, 3, and the pistons at 4:, 4:, 4, 4,connected in any desired manner with the brakes which they control, sothat the movements of these pistons will simultaneously apply or releasethe brakes connected therewith. 5 represents the main hydraulic cylindershown on an enlarged scale in Figures 2 and 3, and connected with eachof the cylinders, 3, 3, 3, 3, by a main pipe indicated at 6, and branchpipes, 7, 7, 7, constructed in any usual or desired manner. In thisinstance we have shown an oil reservoir, indicated at 8, which isarranged to provide for both the initial filling or bleeding of thesystem, and also for automatically maintaining the system filled, andfor venting the system of air, and for compensating for the expansionand contraction of the liquid under changes of temperature. As indicatedin Fig. 2, the main hydraulic cylinder is preferably supported in aninclined position, so that the end occupied by the main hydraulicpiston, 9, when in retracted position, as shown in Fig. 2, is higherthan the outer end of the cylinder, 5, so that a small space, indicatedat 10, in Fig. 2, may be provided at the highest point of the cylinder,forward of the piston, 9, where particles of occluded air may collectwhen the piston is in ofl position. The system is so arranged that thispoint is the highest point of the entire system and therefore as thepressure cylinder is at all times in free and unobstructed communicationwith pipe, 6, and through it with every part of the system, all airoccluded in the oil throughout the entire system will gradually andeventually work to this point.

The oil reservoir, 8, is located above the main hydraulic cylinder, 5,and may be conveniently formed integrally therewith, as shown in Figs. 2and 3, being provided preferably with a removable cover plate, 11,having a filling aperture, 12, closed by a removable cap, 13, providedwith the usual vent holes, 13", in the cap, said cap having 'a partextending into the reservoir and provlded with a baflle plate ordeflector, 13, to prevent the oil from splashing out of the vent .holes,13", in the cap. The hydraulic cylinder, 5, is rovided with a ventingcompensating and ing aperture, or apertures, indicated at 14, located inthe wall of the cylinder at the highest point and just forward of thepiston, 9, when in retracted position, so that any air collecting in thespace indicated at 10, may bubble up through the holes, 14, and thelarge body of oil indicated at 15, in the oil reservoir, to the surfacethereof. It will also be seen that the first movement of the hydraulicpiston, 9,"in the direction of the arrow in Fig. 2, will have the elfectof forcing out some oil and any air in the space indicated at 10, whichair will be forced upward through the body of oil in the reservoir,8,'so that the natural operation of the hydraulic piston, 9, will freethe system from occluded air. It will also be seen that on the returnstroke of the piston, 9, under the power of the actuator, a slightrarification will be produced within the cylinder, 5, and as soon as thepiston, 9, uncovers the apertures or ports, 14, oil from the large bodyof oil, 15, in the reservoir, will be sucked or will flow in to replacethe oil previously forced out of holes, 14, or any oil lost, andautomatically keep the system full. It is important and desirable thatthe port or ports, 14, should communicate directly with a large body ofoil of greater diameter horizontally than the port or ports, instead ofwith a pipe of small diameter, so that the air bubbles which are forcedfrom the hydraulic cylinder by the forward movement of the piston, 9,will pass at once to the surface of the oil in the reservoir and not bedrawn back into the cylinder upon the return of the piston, 9, when oilis admitted to the cylinder from the reservoir, to keep the system full.We therefore prefer to mount the oil reservoir directly upon or veryclosely adj acent to the hydraulic cylinder, 5. We wish it to beunderstood, however, that good results may be obtained by providing acommunicating pipe or passage of large diame ter between the oilreservoir and the port or ports, 14, if it should be desired to locatethe 011 reservoir at a distance from the cylinder,

, 5, so thata large body of oil is provided, into which the air bubblesmay be forced and pass rapidly to the surface of the oil in thereservoir. In such instance, however, such pipe or passage of largediameter would constitute a part of the reservoir,rather than aconnection between the reservoir and the port or ports, 14.

In a hydraulic braking system, it is necessary to fill the system withoil either at the factory when the system is assembled or each time itis necessary to disassemble the system, in whole or in part, forrepairs. To take care of the latter case, it is usual to providehydraulic brake systems with a separate oil pump other than the pump orplunger used to build up the ressures and supply the liquid to apply thebrakes. We propose to eliminate such extra pump in our system and tosupply the necessary oil for filling the system from an oil reservoir,which may be the oil reservoir, 8, as shown in Fig. 2. In this instance,the reservoir, 8, is shown connected by a short pipe line, indicated at16, with the main hydraulic power line, 6, and in the pipe or passage,16, we provided, preferably, a

length, forcing the oil into the branch lines,

7, connected with the pipe, 6. The ends of the lines are then closed bythe fingers, or other-- wise, while the piston, 9, is retracted, eitherby-hand or power, as hereinafter described. Oil will be drawn from thereservoir, 8, through the check valve, 17, pipe, 16, and the adjacentportion of pipe, 6, into the main hydraulic cylinder, 5. The piston, 9,is again moved outwardly in the direction of the arrow in Fig. 2,forcing the oil into the branch lines, and this operation is repeateduntil the entire system, including the main hydraulic cylinder, 5, themain pipe, 6, branch lines, 7, and the hydraulic brake actuatingcylinders, 3, are filled. On the forward stroke of the piston, 9, thecheck valve, 17 will obviously close, and prevent the return of oil intothe reservoir, and insure it being forced into the system. 4

The purpose of the shut off valve is to prevent oil being sucked intothe system when the brakeshave'been released, after theyhave beenapplied for the operation of the main hydraulic piston, either by handor by power, as hereinafter described. It will be understood that thebrakes areboth positively applied and positively released by theirrespective pistons, 4. On the return stroke of the main hydraulicpistons, 9, a partial vacuum is created in the main cylinder, 5, whichwithdraws the oil from the brake applying cylinders, 3. If the shut offvalve, 18, were open during such retracting movement of the mainhydraulic piston, 9, some oil would be sucked into the cylinder, 5, fromthe reservoir, through the pipe or passage, 16, and this i would preventthe brakes from being completely released, if the port or ports, 14,were not provided for the automatic filling of the system, and wetherefore prefer, to provide the shutoff valve, or passage, 16; where,however, as shown in Fig. 2, the port or ports, 14, are provided in themain hydraulic cylinder, the shut off valve in any case,

18, in the pipe could be dispensed with, if desired, where the pipe, 16,and ports, 14, are connected to a common reservoir or reservoirs, as anyoil sucked into the cylinder through the check valve on the returnstroke of the piston, would be forced out of the cylinder, 5, throughthe port or ports, 14, as soon as the latter are uncovered by thepiston, 9, by the action of the retracting springs with which the brakemechanisms are provided, as a matter of common practice, such springsbeing indicated for example, at 19 in Fig. 1. We prefer, however, asbefore stated, to provide the shut ofi valve, 18, so that it can beused, if desired.

e wish it to be understood that the po wer for operating the main hdraulic piston, 9, may be physlcal power 0 the operator, exerted throughan ordinary foot lever or hand lever, or otherwise, or it may besupplied as indicated in the accompanying drawing, by power. In thepresent instance, we have shown an arrangement wherein the mainhydraulic piston, 9, may be operated by power under the control of theoperator, the power being supplied from the intake manifold of theengine, or directly by the physical power of the operator on failure ofpower for any reason. For this purpose we have shown, in connection withthe maimhydraulic cylinder, 5, a power actuator substantially of thekind illustrated in our former application for Let ters Patent of theUnited States, filed December 22, 1923, Serial No. 682,346, although thespecific valve mechanism for the actuator herein shown difi'ers somewhatfrom that shown in our former application above referred to. This valvemechanism, however, forms no part of the present invention. Aspreviously stated, the actuator comprises a cylinder, 20,'closed at bothends by heads, 21, one of which is shown provided with a threadedextension, 22, engaged by an internally threaded portion, 23, on thehydraulic cylinder, 5, so that the cylinders,

. 20, and 5, are connected and maintained in co-axial relation. Theactuator cylinder is provided with a piston, 24, the hub, 34, of whichis provided with a hollow piston rod, 35, extending through a stuflingbox, 36, into the hydraulic cylinder 5, where it is connected with thepiston, 9, thereof, in any desired manner, in this instance by means ofa stud, 37, connecting the piston rod, 35, with the head of the mainhydraulic piston, 9. The opposite end of the piston hub, 34, of theactuator, may also be provided with a hollow sleeve, 38, extendingthrough a stufling box, 39, in the adjacent head, 21. The piston hub,34, is also provided with a suction chamber, 25 adapted to be placed incommunication with the actuator cylinder on both sides of the piston bymeans of ports, indicated.at 26 and 27, for example, communicating withvalve chambers, 28 and 29, respectively, on opposite sides of thesuction chamber, 25.

The valve chamber, 28, is provided with conical valve seats, indicatedat 30 and 31, engaged b oppositely disposed valves, 40 and 41,yieldingly pressed in op osite directions by a eushionlng device, 50. hevalve chamber, 29, is provided with valve seats, 32 and 33, engaged byvalves, 42 and 43, respectively, yieldingly pressed in oppositedirections by a cushioning device 50.

44 represents a longitudinally movablevalve actuating sleeve extendingthrough the sleeve, 38, the hub of the piston, 24, and through thehollow piston rod, 35, the outer end of the sleeve, 38, being providedwith a collar, indicated at 45, forming a guide for the sleeve, 44, andprovided with air inlet apertures, 45. This valve actuating sleevepasses through all of the valves, 40, 41, 42 and 43, and is providedwith collars, indicated at 40*, 41, 42 and 43, secured thereto, foractuating these valves, the said collars being so arranged that when thesleeve is in its normal or ofi position, in which it will be arrested bythe engagement of the foot lever with the usual stop, 46, when thelatter is returned to normal or retracted position, the valves, 41 and42, will be held off their seats, while the valves, 40 and 43,will beheld seated. The sleeve, 44, is provided with a plurality of apertures,indicated at 47, communicating with the suction passage, 25, beyondwhich the interior of the sleeve is provided with a plug, indicated at48, separating the opposite end portions of the sleeve.

The piston hub, 34, is provided with an air chamber, 51, at its innerend (at the right,

Fig. 2), connnunicating with the atmosphere by means of aperturesindicated at 52, in the portion of the hollow piston rod, 35, whichextends into the hydraulic cylinder, 5, the latter being provided withone or more breathing apertures, indicated at 53, com-' municating withthe atmosphere in rear of the piston, 9. The opposite end of the hub,34, of the actuator piston, is also provided with an air chamber, 54,communicating with the atmosphere through the space between the sleeve,38, and the sleeve, 44, by means of apertures, 45.

The valve actuating sleeve, 44, is connected by a suction pipe orpassage, 55, with the intake manifold of the engine, and said pipe orpassagev is preferably provided with an adjustable regulating valve, 60,and a check valve. 61, between the regulating valve, 60, and theactuator. The said valve actuating sleeve is also provided with anattaching device or eye, 56, by which it is connected to a suitableoperator operated device. In this instance, I have shown a foot lever,57, mounted on the chassis, 1, and connected by a. link, 58, with thevalve actuating sleeve, the said foot lever being provided with aretracting spring, 59.

In the form of actuator herein shown, the

valves, 41, 42, of the reversing valve mechanism being normally held inopen osition, the actuator cylinder, 20, is connecte on both sides ofthe actuator piston with the suction pipe or passage, 55, thusmaintaining a partial vacuum on both sides ofthe piston. If

the operator presses his foot on the foot lever, the valve sleeve, 44,will be moved in the direction of the arrow at the leftof Fig. 2, thusopening the valve, 42, further, closing the valve, 41, and opening thevalve, 40. This connects the actuator cylinder in rear of the piston (tothe right in Fig. 2) with the suction chamber, 25, and connects the airinlet chamber, 54, with the cylinder on the opposite side of the piston,causin the piston to move to the right in Fig. 2, an imparting a similarmovement to the main hydraulic piston, 9. As the actuator cylinder inrear of the piston was already exhausted, the movement of the actuatorpiston to apply the brakes will not withdraw any material quantity ofair from the actuator cylinder, and the operation of the engine will notbe affected. The first portion of the movement of the piston, 9, closesthe port or ports, 14, as before described, having previously forced outany occluded air through said port or ports, and the oil in the mainhydraulie cylinder, 5, will then be forced through the pipe, 6, andbranch pipes, 7, into the brake actuating cylinder or cylinders, 3, andapply the brakes. The movement of the piston overtakes the movement ofthe valve actuating sleeve, 44, as soon as the movement of the latterstops, and restores the actuator to a balanced condition by closing thevalve, 40, and opening the Valve, 41. When the foot lever is released,the retracting spring efi'ects its return movement, causing the valvesleeve to move in adirection opposite to that of the arrow at the leftin Fig. 2, closing the valve, 42, and opening the valve, 43, to admitatmospheric air in rear of the piston, while the forward portion of theactuator cylinder is connected with the suction pipe, and restoring theparts to normal or off position, thereby retracting the main hydraulicpiston, 9, and releasing the brakes. During the return movement of theactuator piston, the air previously admitted forward of the piston toapply the brakes, will be withdrawn through the suction pipe, 55, andwill be distributed gradually into the intake manifold of the engine, bythe regulating or restricting valve, 60, so as not to interfere with theoperation of the engne.

We also prefer to provide means, permit ting lost motion, for connectingthe operator operated device, or foot lever, with the actuator piston,so that the operator may add his physical force to that of the actuatorwhen desired, and so that the operator may operate by his physical forcethe actuator piston and the hydraulic piston in case of failure of nism.When the brakes have been fully applied by the actuator and mainhydraulic piston in the manner previously described, the operator may,by still further depressing the foot lever, bring the end of the sleeve,44,

into engagement with the shoulder, 63, and

apply his physical force to the hydraulic piston, 9. In case of failureof power for any reason, it will also be seen that the operator may, bythis means, directly actuate the main hydraulic piston, 9, in eitherdirection, by means of the foot lever and its retracting spring.

It is to be understood that in carrying our invention into effect themain hydraulic piston is double acting, that is to say, is positivelyoperated in both directions. As be fore stated, it may be operated inboth directions manually or may be operated in one direction manually,or by power, and in the opposite direction by a retracting spring, or itmay be operated in both directions by power. In the embodiment of ourinvention which we have selected for purposes of illustration, and haveshown and described therein, the main hydraulic piston is arranged to benormally operated in both directions by the doubleacting piston of ourpower actuator and on failure of power it may be operated in onedirection manually and in the other by a retracting sprin but we do notlimit ourselves to the speci c operating means.

What we claim and desire to secure by Letters Patent is 1. In ahydraulic brake system, the combination with a main hydraulic cylinderand a main hydraulic piston therein, said cylinder being provided with aventing port adjacent to the position of the piston when in retractedposition, of an oil reservoir-located above saidcylinder andcommunicating therewith, so as to provide a large body of oil of greaterdiameter, horizontally, than said ort, immediately adjacent thereto,into which occluded air may pass directly to the surface of the oil inthe reservoir, to prevent said air from being returned to the cylinder,a hydraulic actuating cylinder and piston, pipe connections between saidmain hydraulic cylinder and the actuating cylinder, and operatoroperated means for. controlling the movement of said main hydraulicpiston, said oil reservoir being provided with a 7 system, and a checkvalve in said passa communicating-with the main hydraulic cylinderadjacent to its discharge end, to provide for the filling or bleeding ofthe hydraulic system, and a check'valve for preventing the returnmovement of the liquid through said passage, whereby any excess oildrawn throu h said passage on the return movement of the main hydraulicpiston, in normal operations expelled through said port the reservoir.

2. In a hydraulic brake system, the combination with a main hydrauliccylinder and piston, said cylinder being provided with a port adjacentto the position of the piston when in retracted position, an oilreservoir communicatin with said port and located above the saidcylinder, a hydraulic brake actuating cylinder, a piston therein, brakemechanism operatively connected therewith, and retracting means for saidbrake mechanism, and pipe connections between said main and actuatingcylinders, said'reservoir being. provided with a communicating passageextending therefrom to the main hydraulic cylinder adjacent to thedischarge end of the same, for filling or bleeding the system, and acheck valve in said passage for preventing the return of the liquid tothe reservoir through said passage, whereby any liquid drawn into thesystem through said passage, by the return stroke of the main hydraulicpiston in normal operations thereof, will be expelled through said port,when the piston is in off position, by the retracting means for saidbrake mechanism.

3. In a hydraulic brake system, the combination with a main hydrauliccylinder and piston, said cylinder being provided with a port adjacentto the. position of the piston when in retracted position, an oilreservoir communicating with said port and located above the saidcylinder, a hydraulic brake actuating cylinder, a piston therein, brakemechanism operatively connected therewith, and retracting means for saidbrake mechanism, and pipe connections between said main and actuatingcylinders, said reservoir being provided with a communicating passageextending therefrom to the main hydraulic cylinder adjacent to thedischarge end of the same, for filling or bleeding the passage-forpreventing the return of the liquid to the reservoir through saidpassage, and a shut off valve in said passage for preventing the passageof any liquid therethrough during the normal operations of the mainhydraulic piston.

4. In a hydraulic brake system, the combination with a main hydrauliccylinder, a main hydraulic piston working therein, said cylinder beingprovided with a venting and filling port on its upper side, adjacent tothe position of the piston when in retracted poand returned to thereof,may be hydraulic cylinder to sai sition, and adapted to be closed by thefirst part of the active stroke of the piston, a

quid reservoir located above said cylinder and communicating with saidport by means providing a body of oil of reater horizontal diameter thansaid port, adjacent thereto, to permit the escape of occluded airthrough said liquid to the surface of the liquid in the reservoir, anddrawn back into said cylinder in maintaining the system in filledcondition, ahydraulic brake actuating cylinder, a iston therein, brakemechanism connected w1th said piston, pipe connections extendin from themain brake actuating cylinder, a pipe connecting said reservoir with thesystem ad'acent to the discharge end of said main hy raulic cylinder,for filling or bleeding the system, a check valve in said pipe forpreventing the return of liquid therethrough to. the reservoir, a shutofl' valve in said connectingI pipe, and means for operating the mainydraulic piston.

5. In a hydraulic brake system, the combination with a main hydraulic clinder and piston, a brake actuating hydraulic cylinder and piston,brake mechanism connected with said latter piston, and pipe connectionsfrom the main hydraulic cylinder to said brake actuating cylinder, aliquid reservoir, said reservoir being provided with a passage extendingtherefrom-and communicating with the main hydraulic cylinder adjacent tothe discharge end thereof, for filling or bleeding the system, a checkvalvein said passage for preventing the return of liquid therethrough tothe reservoir, and a shut off'valve in said passa e.

6.. n a hydraulic brake system, the combination with a main hydrauliccylinder and piston, a brake actuating hydraulic cylinder and piston,brake mechanism connected with said latter piston, and ipe connectionsfrom the main hydraulic cyhnder to said brake actuating cylinder, aliquid reservoir, a pipe connecting said reservoir with thepipeconnections extending from the main hydraulic cylinder to the brakeactuating cylinder, and connected thereto adjacent to the discharge endof the main hydraulic cylinder, a check valve in said pipe forpreventing the return of liquid therethrough to the reservoir, and ashut off valve in said pipe.

7. In a hydraulic brake system, the combination with a main hydrauliccylinder, and a main hydraulic piston therein, said cylinder beingprovided w1th a venting compensating and fillingport adjacent to theposition of the piston when in retracted position, a liquid reservoirlocated above said cylinder and communicating with said port and withthe atmosphere above the liquid level in the reservoir to provide forventing the entire system connected with said cylinder, and compensatingfor the expansion and contraction prevent said air from being reservoirbeing provide with a liquid pas-.

sage extending therefrom and connected to the system between theposition of the main hydraulic piston when substantially at the end ofits power stroke, and the brake actuating piston, and independently ofthe said port, to provide for filling the system without regard to theposition of the main hydraulic piston in its cylinder, and a check valvein said passage to prevent the return of liquid therethrough to thereservoir.

8. In a hydraulic brake system, the combination with a main hydrauliccylinder, and a main hydraulic piston therein, said cylinder beingprovided with a venting compensating and filling port adjacent to theposi tion of the piston when in retracted position,

, a liquid reservoir located above said cylinder and communicating withsaid port and with the atmosphere above the liquid level in thereservoir to provide for venting the entire system connected with saidcylinder, and compensating for the expansion and contraction of theliquid therein, a hydraulic ac tuating cylinder and piston, pipeconnections between said main hydraulic cylinder and actuating cylinder,constructed to afford free communication at all times in bothdirections, said reservoir being provided with a liquid passageextending therefrom and connected to the system between the position ofthe main hydraulic piston when substantially at the end of its powerstroke, and the brake actuating piston, andindependently of said port,to provide for filling the systemwithout regard to the position of themain hydraulic piston in its cylinder, and a check valve in said passageto prevent the return of liquid therethrough to the reservoir, a poweractuator provided with a double acting piston, connections between saiddouble acting actuator piston and the main hydraulic piston for movingthe latter in both directions, controlling valve mechanism for the poweractuator, and an operator operated part connected with said controllingvalve mechanism.

9. Ina hydraulic brake system, the combination with a main hydrauliccylinder, a main hydraulic piston working therein, said cylinder beingprovided with a venting and filling port on its upper side, adjacent tothe position of the piston when in retracted position, and adapted to beclosed by the first part of the active stroke of the piston, a liquidreservoir located above said cylinder and communicating with said portby means providing a body of oil of greater horizontal diameter thansaid port, adjacent thereto, to permit the escape of occluded airthrough said liquid to the surface of the liquid in the reservoir, andprevent said air from being drawn back into said cylinder in maintainingthe system in filled condition, a hydraulic brake actuating cylinder, apiston therein, brake mechanism connected with said piston, pipeconnections extending from the main hydraulic cylinder to said brakeactuating cylinder, a pipe connecting said reservoir with the systemadjacent to the discharge end of said main hydraulic cylinder, forfilling or bleeding the system, a check valve in said pipe forpreventing the return of liquid therethrough to the reservoir, a shutoflf valve in said connecting pipe, and means for positively moving themainhydraulic piston in both directions.

10. In a hydraulic brake system, the combination with a main hydrauliccylinder, a main hydraulic piston working therein, said cylinder beingprovided with a venting'and filling port on its upper side, adjacent tothe position of the piston when invretracted position, and adapted to beclosed by the first part of the active stroke of the piston, a liquidreservoir located above said cylinder and communicating with said portby means providing a body of oil of greater horizontal diameter thansaid port, adjacent thereto, to permit the escape of occluded airthrough said liquid to the surface of the liquid in the reservoir, andprevent said air from being drawn back into said cylinder in maintainingthe system in filled condition, a hydraulic brake actuating cylinder, apiston therein, brake mechanism connected with said piston, pipeconnections extending from the main hydraulic cylinder to said brakeactuating cylinder, a pipe connecting said reservoir with the systemadjacent to the discharge end of said main hydraulic cylinder forfilling or bleeding the system, a check valve in said pipe forpreventing the return of liquid therethrough to the reservoir, a shutoff valve in said connecting pipe, a power actuator provided with adouble acting piston, connected with the main hydraulic piston foroperating thelatter in both directions, and operator operated means forcontrolling the power actuator piston.

11. In a hydraulic brake system, the combination with a main hydrauliccylinder, a main hydraulic piston working therein, said cylinder beingprovided with a venting and filling port on its upper side, adjacent tothe position of the piston when in retracted position and adapted to beclosed by the first part of the active stroke of the piston, a liquidreservoir located above said cylinder and communicating with said portby means providing a body of oil of greater horizontal diameter thansaid port, adjacent thereto, to permit the escape of occluded airthrough said liquid to the surface of the liquid in the reservoir, andprevent said air from being drawn back into said cylinder in maintainingthe system in filled condition, a hydraulic brake actuating cylinder, apiston therein, brake mechanism connected with said piston pipe,connections extending from the main hydraulic cylinder to said brakeactuating cylinder, a pipe connecting said reservoir with the systemadjacent to the dischar e end of said main actuator a hydraulic cyinderfor filling or bleeding the system, a checkv valve in said pipe forpreventing the return of liquid therethrough to the reservoir, a shutoflf valve in said connecting ipe, a power actuator provided with a dou1e acting piston, connected with the-main hydraulic piston for operatingthe latter in both directions, and operator operated means forcontrolling the power actuator piston, operatively connected with saidactuator piston by means permitting lost motion to effect the operationof the main hydraulic piston in both directions in case of failure ofpower.

12. In a hydraulic brake system, the com- 7 filling orbleeding thesystem, and means for controllin said passage.

13. In a hyd raulic brake system, the combination with a main hydrauliccylinder and piston, a brake actuatlng cylinder and piston, brakemechanism connected with the latter piston, and pipe connectionsconnecting the main hydraulic cylinder and said brake actuating clinder, of a liquid reservoir, said main ydraulic cylinder beinginclined and provided with ports at the highest part capable ofcommunicating with the reservoir when the piston is in released or offposition, said reservoir belng provided with a passage extendingtherefrom and communicating with the main hydraulic cylinder for fillingor bleeding the system, and a check valve in the passage for preventingthe return flow .=of liquid Itherethrough to the reservoir.

14. In a hydraulic brake system, the combination with a main hydrauliccylinder and piston, a brake actuating cylinder and piston, brakemechanism connected with the latter piston, and pipe connectionsconnecting the main hydraulic cylinder and said brake actuatingcylinder, of a power actuator including a cylinder and a piston, adirect connection from the piston of the actuator to the piston in themain hydraulic cylinder, valve mechanism for controlling clifferentialsoffluid pressure to opposite sides of the actuator piston, an operatoroperated part, and a connection between said operator operated part andthe piston in said main hydraulic cylinder by means providing lostmotion, said connection serving to control said valves.

In testimony whereof we aflix our signatures.

CALEB S. BRAGG.

VICTOR W. KLIESRATH.

Ill

